This patent application claims priority on a Japanese patent application, 2001-370545 filed on Dec. 4, 2001, and Japanese patent application, 2001-376423 filed on Dec. 10, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an exposure method, an electron beam exposure apparatus and a fabrication method of an electronic device. More particularly, the present invention relates to an exposure method for exposing a wafer with high precision while correcting a position irradiated with an electron beam.
2. Description of the Related Art
An electron beam exposure apparatus has an electromagnetic lens that can converge an electron beam by using a magnetic field. By using the electromagnetic lens, the electron beam exposure apparatus adjusts a focus of the electron beam with respect to a wafer, thereby adjusting an irradiation position where the wafer is irradiated with the electron beam to a predetermined position.
In recent years, demand for an electron beam exposure apparatus that can expose a wafer having magnetic material with high precision has increased with the increase of finer electronic devices having parts formed of magnetic material such as a magnetic head and an MRAM.
In the conventional electron beam exposure apparatus, however, the irradiation position of the wafer which is irradiated with the electron beam is shifted from a desired position, because the conventional electron beam exposure apparatus adjusts the focus of the electron beam with respect to the wafer by using the electromagnetic lens the magnetic field of which is influenced by the magnetic material of the wafer in a case of exposing the wafer with the magnetic material.
Therefore, it is an object of the present invention to provide an exposure method, an electron beam exposure apparatus and a fabrication method of an electronic device, which are capable of overcoming the above drawbacks accompanying the conventional art. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, an exposure method for exposing a wafer having magnetic material by using an electron beam, comprises: placing the wafer on a wafer stage; calculating a correction value that corrects a deflection amount by a deflector that deflects the electron beam, based on an irradiation position on the wafer on which the electron beam is to be incident and a magnetic field formed by the magnetic material; and deflecting the electron beam based on the correction value to expose the wafer.
The calculation may calculate the correction value further based on a distribution of the magnetic material on or in the wafer.
The calculation may calculate the correction value further based on a wafer-placed position on the wafer stage at which the wafer is placed.
The calculation may calculate the correction value further based on a positional relationship between the wafer and a magnetic field formed by an electromagnetic lens for converging the electron beam.
The calculation may calculate the correction value based on the positional relationship between the wafer and the electromagnetic lens serving as an objective lens.
The calculation may calculate the correction value further based on a shape of the wafer.
The exposure method may further comprise correcting a stage-position that is a position of the wafer stage, and the calculation may calculate the correction value based on the irradiation position on the wafer placed on the wafer stage for which the stage-position has been corrected.
The exposure method may further comprise forming a mark portion on the wafer, and the calculation may calculate the correction value further based on a positional relationship between a position of the mark portion and the irradiation position on the wafer.
The exposure method may further comprise: placing another wafer on the wafer stage; correcting another correction value that corrects the deflection amount by the deflector based on a positional relationship between the wafer-placed position of the wafer on the wafer stage and another wafer-placed position of the other wafer on the wafer stage, and the correction value for the wafer; and deflecting the electron beam based on the other correction value to expose the other wafer.
According to the second aspect of the present invention, an exposure method for exposing a wafer by using an electron beam, comprises: placing the wafer on a wafer stage; calculating a correction value that corrects a deflection amount of the electron beam based on a positional relationship between the wafer and a magnetic field for converging the electron beam; and deflecting the electron beam based on the correction value to expose the wafer.
According to the third aspect of the present invention, an electron beam exposure apparatus for exposing a wafer having magnetic material by using an electron beam, comprises; a wafer stage on which the wafer is to be placed; a deflector operable to deflect the electron beam; and a calculation unit operable to calculate a correction value that corrects a deflection amount of the electron beam by the deflector, based on an irradiation position on the wafer, on which the electron beam is to be incident, and a magnetic field formed by the magnetic material.
The electron beam exposure apparatus may further comprise an electromagnetic lens operable to form a magnetic field to converge the electron beam, and the calculation unit may calculate the correction value further based on a positional relationship between the wafer and the magnetic field formed by the electromagnetic lens.
The electromagnetic lens may serve as an objective lens.
According to the fourth aspect of the present invention, a fabrication method of an electronic device by exposing a wafer having magnetic material by using an electromagnetic lens, comprises: placing the wafer on a wafer stage; calculating a correction value that corrects a deflection amount by a deflector for deflecting the electron beam, based on an irradiation position on the wafer, on which the electron beam is to be incident, and a magnetic field formed by the magnetic material; and deflecting the electron beam based on the correction value to expose the wafer.
The fabrication method of an electronic device may further comprise forming a mark portion including at least a first mark portion in a first region in the wafer, wherein the placing of the wafer places the wafer with the first mark portion therein on the wafer stage, and the calculation calculates the correction value further based on a position of the first mark portion in the wafer.
The fabrication method of an electronic device may further comprise: storing the correction value in the first region; placing other wafer having magnetic material on the wafer stage; and irradiating the first region in the wafer with the electron beam based on the stored correction value in the first region and a position of the other wafer on the wafer stage.
The formation of the mark portion includes: applying resist on the wafer; exposing the resist by irradiating the first region with light to form the first mark portion in the first region; and exposing the resist by irradiating a second region in the wafer with light to form a second mark portion in the second region, and the calculation may calculate the correction value in the first region further based on the position of the first region and calculates the correction value in the second region further based on a position of the second region, and, in the exposure of the wafer, the electron beam may be deflected based on the correction value in the first region in a case where the first region is irradiated with the electron beam, and may be deflected based on the correction value in the second region in a case where the second region is irradiated with the electron beam.
The formation of the mark portion may include forming a plurality of first mark portions in the first region and forming a plurality of second mark portions in the second region, and the calculation calculates the correction value in the first region further based on relative positions of the plurality of first mark portions and calculates the correction value in the second region further based on relative positions of the plurality of second mark portions.
The summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above. The above and other features and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.